Animals living in colder regions have shorter tails and ears compared to animals living in warmer regions. This phenomenon is called:

Crop plants grown in monoculture are

Read the following statements and select the option that represents the correct statements.
$(1)$ Kangaroo rats never drink water.
$(2)$ Birds undergo hibernation to escape adverse environmental conditions.
$(3)$ Thermal adaptation can be explained by Allen's Rule.
$(4)$ Opuntia possesses phylloclade for protection.

In most animals,the metabolic reactions proceed in a $A$ temperature range (in humans,it is $37^{\circ} C$). But there are microbes (archaebacteria) that flourish in hot springs and deep sea hydrothermal vents where temperatures far exceed $B$. Choose the correct option for $A$ and $B$.

What is a tree line?

The term 'niche' of a species refers to: